Adhesive composition, circuit connecting material, connecting structure for circuit member, and semiconductor device

ABSTRACT

The adhesive composition of the invention comprises a thermoplastic resin, a radical polymerizing compound, a radical polymerization initiator and a radical polymerization regulator. According to the present invention it is possible to provide an adhesive composition, a circuit connecting material, a connection structure for a circuit member and a semiconductor device whereby curing treatment can be carried out with sufficient speed at low temperature, curing treatment can be carried out with a wide process margin, and adequately stable adhesive strength can be obtained.

The application is a Continuation application of application Ser. No.11/629,068, filed Dec. 7, 2007, the contents of which are incorporatedherein by reference in their entirety. Ser. No. 11/629,068 is a NationalStage Application, filed under 35 USC 371, of International (PCT)Application No. PCT/JP2005/010497, filed Jun. 8, 2005.

TECHNICAL FIELD

The present invention relates to an adhesive composition, a circuitconnecting material, a connection structure for a circuit member and asemiconductor device.

BACKGROUND ART

As conventional adhesives for semiconductor elements and liquid crystaldisplay units there have been used thermosetting resins such as epoxyresins, which have excellent adhesive properties and exhibit their highadhesion even under high-temperature, high-humidity conditions (forexample, see Patent document 1). Such adhesives are heated at 170-250°C. for 1-3 hours for hardening to produce their adhesive properties.

The increasing integration of semiconductor elements and higherprecision of liquid crystal devices in recent years have resulted inever narrowing pitches between elements and wiring.

When such adhesives are used for semiconductor elements and the like,the high temperatures for curing and the slow curing speeds result inheating not only at the desired connections but also at surroundingmembers, tending to produce damage and the like in the surroundingmembers.

Throughput must be improved for cost reduction, and therefore a demandexists for adhesion at low temperature (100-170° C.) and in shortperiods (within an hour), i.e. “low-temperature fast curing”.

On the other hand, recent years have seen increasing interest in radicalcuring adhesives combining acrylate derivatives or methacrylatederivatives with peroxides as radical polymerization initiators. Curingand bonding of such adhesives is accomplished by polymerization reactionof radicals as reactive species with excellent reactivity, therebyallowing curing in relatively short time periods (for example, seePatent document 2).

-   [Patent document 1] Japanese Patent Application Laid-Open No.    H01-113480-   [Patent document 2] Japanese Patent Application Laid-Open No.    2002-203427

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, the excellent reactivity of radical curing adhesives tends toresult in a narrower process margin for curing treatment. For example,when such radical curing adhesives are used for electrical connection ofsemiconductor elements or liquid crystal display units, even slightvariation in the process conditions such as temperature and time forobtaining the cured adhesives will generally make it impossible toobtain stable adhesive strength.

It is therefore an object of the present invention to provide anadhesive composition, a circuit connecting material, a connectionstructure for a circuit member and a semiconductor device whereby curingtreatment can be carried out with sufficient speed at low temperature,curing treatment can be carried out with a wide process margin, andadequately stable adhesive strength can be obtained.

Means for Solving the Problems

The adhesive composition of the invention that solves the problemsdescribed above comprises a thermoplastic resin, a radical polymerizingcompound, a radical polymerization initiator and a radicalpolymerization regulator.

This type of adhesive composition allows curing treatment to be carriedout with sufficient speed at low temperature, and permits curingtreatment with a wide process margin while obtaining adequately stableadhesive strength.

The radical polymerization regulator preferably contains an aminecompound having a divalent organic group represented by the followinggeneral formula (A).

Specifically, the adhesive composition preferably comprises athermoplastic resin, a radical polymerizing compound, a radicalpolymerization initiator and an amine compound having a divalent organicgroup represented by the following general formula (A).

In formula (A), X¹, X², X³ and X⁴ independently represent hydrogen orC1-5 alkyl.

The adhesive composition of the invention is a radical curing adhesivecomposition comprising a thermoplastic resin, a radical polymerizingcompound, a radical polymerization initiator and an amine compound. Suchan adhesive composition containing a radical polymerizing compound ishighly reactive and can therefore be cured in a sufficiently shortperiod even at low temperature. By using an amine compound representedby general formula (1), it is possible to widen the process margin forcuring treatment. Cured products obtained from the adhesive compositioncan exhibit stable adhesive strength even with variation in the processtemperature or time used to obtain the cured products. It is alsopossible to prevent reduction in the adhesive strength of the curedadhesive composition with passage of time.

Since the use of such an adhesive composition according to the inventionallows curing treatment to be accomplished in a short period and canwiden the process margin, even when the pitch between elements andwirings of semiconductor elements or liquid crystal devices is narrow itis possible to prevent heating at surrounding members instead of only atthe desired connections, which causes damage and the like in thesurrounding members, and therefore the throughput can be improved.

The radical polymerization regulator is preferably represented by thefollowing general formula (1).

In formula (1), R¹ and R² each independently represent hydrogen,hydroxyl or a monovalent organic group, and X¹, X², X³ and X⁴ eachindependently represent hydrogen or C1-5 alkyl.

If the amine compound is represented by general formula (1) above, theprocess margin for curing treatment can be widened even further.

More preferably, R¹ is hydrogen, hydroxyl, C1-10 alkyl, aryl, C2-20alkoxy, or a monovalent organic group represented by the followinggeneral formula (2).

In formula (2), R³ represents hydrogen or C1-5 alkyl, R⁴ represents C1-5ester, benzyl ester, carboxyl or aryl, R⁵ represents hydrogen, C1-20alkyl, C1-20 alkoxy, phenoxy, aryl, C1-20 carbonyloxy, phenylcarbonyloxyor vinyl and n represents an integer of 1-20, where phenoxy, aryl andphenylcarbonyloxy may be optionally substituted with C1-5 alkyl.

If R¹ is hydrogen, hydroxyl, C1-10 alkyl, aryl, C2-20 alkoxy or a grouprepresented by general formula (2) above, the process margin for curingtreatment can be widened yet further.

The radical polymerization regulator preferably has at least oneaminoxyl structure in the molecule. Since the radical polymerizationregulator exists as a stable radical even in air, it provides theadvantage of improved storage stability.

The radical polymerizing compound in the adhesive composition of theinvention preferably has two or more (meth)acryloyl groups in themolecule. Using such an adhesive composition will allow curing treatmentto be accomplished in an even shorter period of time. The presentinventors attribute this to the fact that the radical polymerizingcompound has two or more (meth)acryloyl groups as highly reactiveradical reactive groups.

Furthermore, since the radical polymerizing compound uses a(meth)acryloyl group as the reactive group, it is possible to obtainfirm adhesion regardless of the material of the adherend. Thus, theadhesive composition of the invention comprising such a radicalpolymerizing compound has high general utility, and can provide morestable adhesive strength when used for semiconductor elements and liquidcrystal display units, for example.

The radical polymerization initiator is preferably a peroxy esterderivative having a one-minute half-life temperature of 90-175° C. Here,a “one-minute half-life temperature” is the temperature at which thehalf-life is one minute, and the “half-life” is the time in which thecompound concentration is reduced to half its initial value.

If the one-minute half-life temperature of the radical polymerizationinitiator is 90-175° C., the cured product obtained from the adhesivecomposition of the invention will be able to exhibit more excellentconnection resistance compared to conventional products. It will also bepossible to prevent reduction in the connection resistance of the curedadhesive composition with passage of time.

The radical polymerization initiator is preferably a peroxy esterderivative with a molecular weight of 180-1000. If the radicalpolymerization initiator is a peroxy ester derivative and its molecularweight is within the numerical range stated above, its compatibilitywith other radical polymerizing compounds will be excellent and theobtained cured product will exhibit more stable properties such asadhesive strength and connection resistance throughout the entireproduct.

The adhesive composition of the invention preferably contains theradical polymerizing compound at 50-250 parts by weight, the radicalpolymerization initiator at 0.05-30 parts by weight and the radicalpolymerization regulator at 0.001-30 parts by weight with respect to 100parts by weight of the thermoplastic resin. The adhesive composition ofthe invention can exhibit a more notable effect of the invention if theconstituent materials are added within the ranges specified above.

The adhesive composition also preferably contains conductive particles.Such an adhesive composition will exhibit conductivity. This will allowthe adhesive composition to be used as a conductive adhesive in fieldssuch as electrical and electronic industries for circuit electrodes,semiconductors and the like. A conductive adhesive composition can alsoreduce connection resistance after curing.

The proportion of conductive particles added is preferably 0.5-30 partsby weight of the conductive particles with respect to 100 parts byweight of the thermoplastic resin. An adhesive composition havingconductive particles added within this range will be able to more fullyexhibit the effect of the conductive particles. When used for connectionof circuit electrodes, for example, it is possible to prevent lack ofconduction between opposing circuit electrodes or shorting betweenadjacent circuit electrodes. In addition, the adhesive compositioncontaining conductive particles in the proportion described aboveexhibits electrical connection anisotropy, and can be used as ananisotropic conductive adhesive composition.

The circuit connecting material of the invention is a circuit connectingmaterial for electrical connection between opposing circuit electrodes,and the circuit connecting material is characterized by comprising theaforementioned adhesive composition.

This type of circuit connecting material can sufficiently shorten thetime period for bonding between opposing circuit electrodes even at lowtemperature, and can widen the process margin. Cured products obtainedfrom the circuit connecting material can exhibit stable adhesivestrength even with variation in the process temperature or time used toobtain the cured products. It is also possible to prevent reduction inthe adhesive strength of the cured circuit connecting material withpassage of time. Furthermore, if the circuit connecting materialcontains conductive particles in the proportion mentioned above, it canexhibit electrical connection anisotropy and can be used as ananisotropic conductive circuit connecting material for circuitelectrodes.

The adhesive composition or circuit connecting material described aboveis preferably formed into a film. A film-like adhesive composition orcircuit connecting material has excellent handleability and cantherefore further improve the throughput.

When opposing circuit members are bonded by heating under conditionswith a compression time of 10 seconds, a pressure of 3 MPa and a heatingtemperature of 140-200° C., the maximum value of the connectionresistance between the heat bonded connection members in the entireheating temperature range is preferably no greater than 3 times theminimum value. This will allow the process margin to be further widened.

The connection structure for a circuit member of the invention is aconnection structure for a circuit member comprising a first circuitmember having a first circuit electrode formed on the main side of afirst circuit board, a second circuit member having a second circuitelectrode formed on the main side of a second circuit board, and acircuit connecting member formed between the main side of the firstcircuit board and the main side of the second circuit board, whichelectrically connects the first circuit electrode and second circuitelectrode positioned opposite each other, characterized in that thecircuit connecting member is a cured product of the aforementionedcircuit connecting material.

This type of connection structure for a circuit member allowselectrically connected circuit electrodes to be effectively utilized.That is, since the aforementioned circuit connecting material is used toallow electrical connection between the first circuit electrode andsecond circuit electrode, a circuit member having the connectionstructure of the invention has little quality variation and exhibitssufficiently stable properties. Furthermore, a cured product of thecircuit connecting material containing conductive particles can lowerthe connection resistance. Addition of conductive particles can preventloss of conduction between opposing circuit electrodes or shortingbetween adjacent circuit electrodes. If the conductive particles areadded in the proportion mentioned above, it is also possible to achieveelectrical connection anisotropy to obtain an anisotropic circuitconnecting material.

The semiconductor device of the invention is a semiconductor devicecomprising a semiconductor element, a base on which the semiconductorelement is mounted, and a semiconductor element connecting memberprovided between the semiconductor element and the base and electricallyconnecting the semiconductor element and the base, characterized in thatthe semiconductor element connecting member is a cured product oradhesive film made of the aforementioned adhesive composition.

Since the cured product of an adhesive composition electricallyconnecting the semiconductor element and the base in the semiconductordevice as described above is a cured product of the aforementionedadhesive composition, it has little quality variation and can exhibitsufficiently stable properties. Furthermore, a cured product of theadhesive composition that contains conductive particles can lower theconnection resistance. Addition of the conductive particles canadequately ensure conductivity between the opposing semiconductorelement and base. If the conductive particles are added in theproportion mentioned above, it is also possible to achieve electricalconnection anisotropy to obtain an anisotropic semiconductor.

Effect of the Invention

According to the present invention it is possible to provide an adhesivecomposition, a circuit connecting material, a connection structure for acircuit member and a semiconductor device whereby curing treatment canbe carried out with sufficient speed at low temperature, curingtreatment can be carried out with a wide process margin, and adequatelystable adhesive strength can be obtained.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a simplified cross-sectional view showing an embodiment of aconnection structure for a circuit member according to the invention.

FIG. 2 is a simplified cross-sectional view showing an embodiment of asemiconductor device according to the invention.

EXPLANATION OF SYMBOLS

1: Connection structure for a circuit member, 2: semiconductor device,7: conductive particles, 10: circuit connecting member, 11: insulatingsubstance, 20: first circuit member, 21: first circuit board, 22: firstcircuit electrode, 30: second circuit member, 31: second circuit board,32: second circuit electrode, 40: semiconductor element connectionmember, 50: semiconductor element, 60: base, 61: circuit pattern, 70:sealing material.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the invention will now be explained withreference to the accompanying drawings where necessary. Correspondingelements will be referred to by like reference numerals and will beexplained only once. Throughout the following explanation,“(meth)acrylate” means “acrylate” or its corresponding “methacrylate”.

(Adhesive Composition)

The adhesive composition of the invention comprises a thermoplasticresin, a radical polymerizing compound, a radical polymerizationinitiator and a radical polymerization regulator. This type of adhesivecomposition allows curing treatment to be carried out with sufficientspeed at low temperature, and permits curing treatment with a wideprocess margin while obtaining adequately stable adhesive strength.

Each of the components will now be explained in detail.

[Radical Polymerization Regulator]

The radical polymerization regulator for the invention may be anypublicly known one without any particular restrictions, so long as it isa compound that rapidly reacts with the initiating radical generated bydecomposition of the radical polymerization initiator such as a peroxideduring heat curing, or with the growth radical produced when theinitiating radical attacks the radical polymerizing compound, andreproduces the radical by heating at 60° C. or above to promotepolymerization of the radical polymerizing compound.

Preferred among these are amine compounds with a divalent organic grouprepresented by the following general formula (A).

In formula (A), X¹, X², X³ and X⁴ each independently represent hydrogenor C1-5 alkyl. Here, “alkyl” includes not only straight-chain alkyl butbranched and cyclic alkyl groups.

By using an amine compound represented by general formula (A) above, itis possible to widen the process margin for curing treatment. Curedproducts obtained from the adhesive composition can exhibit stableadhesive strength even with variation in the process temperature or timeused to obtain the cured products. It is also possible to preventreduction in the adhesive strength of the cured adhesive compositionwith passage of time.

Since the use of such an adhesive composition according to the inventionallows curing treatment to be accomplished in a short period and canwiden the process margin, even when the pitch between elements andwirings of semiconductor elements or liquid crystal devices is narrow itis possible to prevent heating at surrounding members instead of only atthe desired connections, which causes damage and the like in thesurrounding members, and therefore the throughput can be improved.

The amine compound is preferably one represented by the followinggeneral formula (1). Using such a compound as the amine compound canfurther widen the process margin for curing treatment.

In formula (1), R¹ and R² each independently represent hydrogen,hydroxyl or a monovalent organic group, and X¹, X², X³ and X⁴ eachindependently represent hydrogen or C1-5 alkyl. An organic group is acarbon-containing substituent, and there are no particular restrictionson the rest of the structure of the substituent. As monovalent organicgroups to be used as R² there are preferred C1-10 alkyl, aryl, C2-20alkoxy, ether and ester groups. Methyl may be mentioned as an example ofa C1-10 alkyl group, and octoxy may be mentioned as an example of aC2-20 alkoxy group. When R² is hydroxyl, the ester group may be obtainedby ester reaction with a monocarboxylic acid such as methacrylic acid or2-methylhexanoic acid, a dicarboxylic acid such as sebacic acid, or atetracarboxylic acid.

R¹ in general formula (1) is preferably hydrogen, hydroxyl, C1-10 alkyl,aryl, C2-20 alkoxy, or a monovalent organic group represented by thefollowing general formula (2). Using such a substituent as R¹ canfurther widen the process margin for curing treatment. Methyl may bementioned as an example of a C1-10 alkyl group, and octoxy may bementioned as an example of a C2-20 alkoxy group.

In formula (2), R³ represents hydrogen or C1-5 alkyl, R⁴ represents C1-5ester, benzyl ester, carboxyl or aryl, R⁵ represents hydrogen, C1-20alkyl, C1-20 alkoxy, phenoxy, aryl, C1-20 carbonyloxy, phenylcarbonyloxyor vinyl and n represents an integer of 1-20, where phenoxy, aryl andphenylcarbonyloxy may be optionally substituted with C1-5 alkyl.

The reason why a cured product with satisfactorily stable adhesivestrength is obtained using the adhesive composition of the invention isnot fully understood at the current time. As one cause, however, thepresent inventors conjecture that the amine compound stabilizes theradical polymerization reaction, thus yielding a relatively stable curedproduct even when the process conditions vary. However, this is notnecessarily the only reason.

As specific amine compounds there may be mentionedN,N′-bis(3-aminopropyl)ethylenediamine and2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazinecondensate, andpoly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}].In addition, there may be mentioned compounds represented by thefollowing chemical formulas (3)-(11) and (13)-(16), and polymersobtained by introducing a substituent represented by general formula (1)above at a side chain of a polyamine, polyester, polyacrylate or thelike. These compounds may be used alone, or two or more differentcompounds may be used in combination.

In formula (11), R¹⁰ is a group represented by formula (12a) or (12b)below.

In formula (13), m represents a positive integer.

The radical polymerization regulator used for the invention preferablyhas at least one aminoxyl structure in the molecule. Since the radicalpolymerization regulator exists as a stable radical even in air, itprovides the advantage of improved storage stability.

As compounds having the aforementioned aminoxyl structure there may bementioned, specifically, 2,2,6,6-tetramethylpiperidine-1-oxyl,2,2-dimethyl-6-phenylpiperidine-1-oxyl,2,2,6-trimethyl-6-phenylpiperidine-1-oxyl,2,6-diphenylpiperidine-1-oxyl,4-acetamide-2,2,6,6-tetramethylpiperidine-1-oxyl,4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl,4-carboxy-2,2,6,6-tetramethylpiperidine-1-oxyl,3-carboxy-2,2,6,6-tetramethylpiperidine-1-oxyl,4-(2-chloroacetamide)-2,2,6,6-tetramethylpiperidine-1-oxyl,4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl,4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxylbenzoate,4-(2-iodoacetamide)-2,2,6,6-tetramethylpiperidine-1-oxyl,4-isothiocyanato-2,2,6,6-tetramethylpiperidine-1-oxyl,4-isocyanato-2,2,6,6-tetramethylpiperidine-1-oxyl,4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl,4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl,2,2-dimethyl-6-cyclohexylpiperidine-1-oxyl,2,6-dicyclohexylpiperidine-1-oxyl,2,2-dimethyl-6-cyclopentylpiperidine-1-oxyl,2,6-dicyclopentylpiperidine-1-oxyl,2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitrooxide,2,2,5,5-tetramethylpyrrolidine-1-oxyl, 2,5-diphenylpyrrolidine-1-oxyl,2,2-dimethyl-5-phenylpyrrolidine-1-oxyl,2,2,5-trimethyl-5-phenylpyrrolidine-1-oxyl, and the like.

As other compounds with aminoxyl structures there may be mentioned theradical-generating compounds represented by the following generalformulas (17) and (18).

In formula (17), Y¹ and Y² each independently represent C1-5 alkyl suchas isopropyl, t-butyl or the like, aryl, C2-20 alkoxy or C5-10cycloalkyl. The aryl group may be optionally substituted with C1-5 alkylor C1-5 alkoxy.

In formula (18), Y³ and Y⁴ each independently represent a C1-5 alkylenechain.

As other compounds with aminoxyl structures there may be mentioned theradical-generating compounds represented by the following generalformulas (19)-(21), and polymers obtained by introducing an aminoxylstructure at a side chain of a polyamine, polyester, polyacrylate or thelike.

In formula (19), R¹¹ represents a C1-5 alkylene chain or a phenylenechain.

In formula (20), R¹² represents a C1-5 alkylene chain or a phenylenechain.

In formula (21), R¹³ is a group represented by the following formula(12c).

The compound having an aminoxyl structure may be used alone, or two ormore different such compounds may be used in admixture.

The amount of radical polymerization regulator added is preferably0.001-30 parts by weight and more preferably 0.001-10 parts by weightwith respect to 100 parts by weight of the thermoplastic resin. If theamount of radical polymerization regulator added is less than 0.001parts by weight, the effect of addition will tend to be reduced comparedto when the amount of addition is within the range specified above,while if the amount of radical polymerization regulator added is greaterthan 30 parts by weight, the radical polymerization regulator additionbecomes excessive and impairs the curing property while preventingfurther improvement in adhesive strength stabilizing effect, and tendingto reduce compatibility with other radical polymerizing compounds.

From the standpoint of widening the process margin, the amount ofradical polymerization regulator added is preferably 0.01-30 parts byweight with respect to 100 parts by weight of the thermoplastic resin.If the amount of radical polymerization regulator added is less than0.01 part by weight, the radical polymerization regulator addition willbe so low as to impede widening of the process margin, tending to resultin poorer stabilization of the adhesive strength. The amount of radicalpolymerization regulator addition is more preferably 0.01-10 parts byweight and even more preferably 0.05-10 parts by weight with respect to100 parts by weight of the thermoplastic resin.

[Thermoplastic Resin]

The thermoplastic resin of the invention may be used to reinforceadhesion between objects to be bonded (hereinafter referred to simply as“adherends”).

The thermoplastic resin used for the invention may be any publicly knownone, without any particular restrictions. Specifically, there may beused polyamides, phenoxy resins, poly(meth)acrylates, polyimides,polyurethanes, polyesters, polyvinylbutyrals and the like. These may beused alone or in combinations of two or more. The resins may also havesiloxane bonds or fluorine substituents in the molecule. These may besuitably used in a state which produces complete compatibilizationbetween resins, or which produces microphase separation and turbidity.

A larger molecular weight of the thermoplastic resin will allow easierformation of a film as described hereunder, while the solutionviscosity, which affects the flow properties of the adhesive, may be setwithin a wide range. Since the solution viscosity can be set within awide range, attachment of the adhesive onto surrounding members can befurther prevented when the composition is used for connection ofsemiconductor elements or liquid crystal devices even when the pitchbetween elements and wirings is narrow, and therefore the throughput canbe improved. However, a molecular weight of greater than 150,000 willtend to produce inferior compatibility with other components, while amolecular weight of less than 5000 will tend to result in unsatisfactoryfilm formation when the composition is used as a film as describedhereunder. The molecular weight, in terms of weight-average molecularweight, is therefore preferably 5000-150,000 and more preferably10,000-80,000.

[Radical Polymerizing Compound]

The radical polymerizing compound of the invention is a compound havingthe property of generating radicals upon input of energy and forming apolymer by chain reaction polymerization of the radicals. The radicalpolymerization reaction normally proceeds more rapidly than cationpolymerization or anion polymerization. According to the inventionemploying a radical polymerizing compound, it is therefore possible toaccomplish polymerization within a relatively short period of time.

The radical polymerizing compound used for the invention may be anypublicly known one without any particular restrictions, so long as it isa compound having an olefin group in the molecule, such as (meth)acryl,(meth)acryloyl or vinyl, or a compound that polymerizes via radicals,such as styrene derivatives or maleimide derivatives. Preferred amongthese are radical polymerizing compounds having (meth)acryloyl groups,with compounds having two or more (meth)acryloyl groups being morepreferred.

As radical polymerizing compounds with (meth)acryloyl groups there maybe mentioned oligomers such as epoxy(meth)acrylate oligomers,urethane(meth)acrylate oligomers, polyether(meth)acrylate oligomers andpolyester(meth)acrylate oligomers, and polyfunctional (meth)acrylatecompounds such as trimethylolpropane tri(meth)acrylate,polyethyleneglycol di(meth)acrylate, polyalkyleneglycoldi(meth)acrylate, dicyclopentenyl(meth)acrylate,dicyclopentenyloxyethyl(meth)acrylate, neopentylglycol di(meth)acrylate,dipentaerythritol hexa(meth)acrylate, isocyanuric acid-modifiedbifunctional (meth)acrylates, isocyanuric acid-modified trifunctional(meth)acrylates, 2,2′-di(meth)acryloyloxydiethyl phosphate,2-(meth)acryloyloxyethyl acid phosphate, and the like. These compoundsmay be used alone or in combinations of two or more as necessary.

Using a (meth)acryloyl group as the reactive group can produce firmbonding regardless of the material quality of the adherend. As adherendsthere may be mentioned printed circuit boards and polyimide or otherorganic base materials, as well as metals such as copper and aluminum,or ITO (indium tin oxide), silicon nitride (SiN), silicon dioxide (SiO₂)and the like.

The radical polymerizing compound preferably has two or more(meth)acryloyl groups in the molecule, because the heating time requiredfor bonding will be further shortened and the heating temperaturerequired for bonding will be further lowered. This is attributed to alarger number of (meth)acryloyl groups as radical reactive groups in themolecule of the radical polymerizing compound.

The proportion of the radical polymerizing compound added is preferably50-250 parts by weight and more preferably 60-150 parts by weight withrespect to 100 parts by weight of the thermoplastic resin. If theproportion of the radical polymerizing compound added is less than 50parts by weight, the heat resistance of the cured adhesive compositionattached to the adherend will tend to be reduced, and if it is greaterthan 250 parts by weight, the film formation will tend to beunsatisfactory when the adhesive composition is used as a film asdescribed hereunder.

[Radical Polymerization Initiator]

The adhesive composition of the invention comprises a radicalpolymerization initiator. Once the radical polymerization reaction hasbeen initiated, the radical polymerizing compound undergoes a chainreaction to produce rigid curing, but because it is relatively difficultto generate the first radicals, a radical polymerization initiatorcapable of producing radicals relatively easily is included.

The radical polymerization initiator used for the invention may be apublicly known peroxide or azo compound known in the prior art.Specifically, there may be mentioned cumylperoxy neodecanoate,1,1,3,3-tetramethylbutylperoxy neodecanoate,1-cyclohexyl-1-methylethylperoxy neodecanoate, t-hexylperoxyneodecanoate, t-butylperoxy neodecanoate, t-butylperoxy pivalate,1,1,3,3-tetramethylbutylperoxy-2-ethyl hexanoate,2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethyl hexanoate, t-butylperoxy neoheptanoate,t-amylperoxy-2-ethyl hexanoate, di-t-butylperoxy hexahydroterephthalate,t-amylperoxy-3,5,5-trimethyl hexanoate,3-hydroxy-1,1-dimethylbutylperoxy neodecanoate,1,1,3,3-tetramethylbutylperoxy-2-ethyl hexanoate, t-amylperoxyneodecanoate, t-amylperoxy-2-ethyl hexanoate,2,2′-azobis-2,4-dimethylvaleronitrile,1,1′-azobis(1-acetoxy-1-phenylethane), 2,2′-azobisisobutyronitrile,2,2′-azobis(2-methylbutyronitrile),dimethyl-2,2′-azobisisobutyronitrile, 4,4′-azobis(4-cyanovaleric acid),1,1′-azobis(1-cyclohexanecarbonitrile), t-hexylperoxyisopropylmonocarbonate, t-butylperoxymaleic acid ester,t-butylperoxy-3,5,5-trimethyl hexanoate, t-butylperoxy laurate,2,5-dimethyl-2,5-di(3-methylbenzoylperoxy)hexane,t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxy benzoate,2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxy benzoate,dibutylperoxytrimethyl adipate, t-amylperoxy normal-octoate,t-amylperoxy isononanoate, t-amylperoxy benzoate, and the like. Thesecompounds may be used alone, or two or more different compounds may beused in combination.

Preferred among these are peroxy ester derivatives, so that the radicalpolymerization initiator has a one-minute half-life temperature of90-175° C. If the one-minute half-life temperature of the radicalpolymerization initiator is 90-175° C., the cured product obtained fromthe adhesive composition of the invention will be able to exhibit moreexcellent connection resistance compared to conventional products. Itwill also be possible to prevent reduction in the connection resistanceof the cured adhesive composition with passage of time.

Also preferred are peroxy ester derivatives with molecular weights of180-1000. If the radical polymerization initiator is a peroxy esterderivative and its molecular weight is within the numerical range statedabove, its compatibility with other radical polymerizing compounds willbe excellent and the obtained cured product will exhibit more stableproperties such as adhesive strength and connection resistancethroughout the entire product.

The amount of radical polymerization initiator added is preferably0.05-30 parts by weight and more preferably 0.1-20 parts by weight withrespect to 100 parts by weight of the thermoplastic resin. If the amountof radical polymerization initiator added is less than 0.05 parts byweight, the radical polymerization may not be adequately initiated,whereas if the amount of radical polymerization initiator added isgreater than 30 parts by weight, the storage stability will tend to bereduced.

There are no particular restrictions on the form of energy used for theinvention, and there may be mentioned heat, electron beam, gamma rays,ultraviolet rays, infrared rays and the like.

The adhesive composition of the invention also preferably containsconductive particles. Adding conductive particles can conferconductivity to the adhesive composition. This will allow its use as aconductive adhesive in fields such as electrical and electronicindustries for circuit electrodes, semiconductors and the like.

The conductive particles used are not particularly restricted so long asthey have a degree of conductivity permitting electrical connection, andas examples there may be mentioned metals such as Au, Ag, Ni, Cu, solderand the like, or carbon. Alternatively, non-conductive glass, ceramic,plastic or the like may be used as a core covered with theaforementioned metals or carbon. Preferably, the metal itself is aheat-fusible metal, or a plastic core is covered with a metal or carbon.This will further facilitate deformation of the cured adhesivecomposition by heat or pressure, thereby increasing the contact areabetween the electrodes and the adhesive composition when it is used forelectrical connection between electrodes, and improving the conductivitybetween electrodes.

The surfaces of the conductive particles may also be covered with apolymer resin for use as laminar particles. If laminar conductiveparticles are added to the adhesive composition, shorting by contactbetween conductive particles will be further inhibited due to the resincovering even if the amount of conductive particles is increased, andtherefore the insulating property between electrode circuits can beimproved. The conductive particles or laminar particles may be usedalone or in combinations of two or more different types.

The mean particle size of the conductive particles is preferably 1-18 μmfrom the viewpoint of dispersibility and conductivity. The proportion ofconductive particles added is preferably 0.1-30 vol % and morepreferably 0.1-10 vol % with respect to 100 vol % of the adhesivecomposition. If this value is less than 0.1 vol % it may not be possibleto achieve adequate conductivity, and if it is greater than 30 vol %there will be a greater tendency toward circuit shorting. The proportionof conductive particles (vol %) is determined based on the volume ofeach component before curing of the adhesive composition at 23° C., andthe volume of each component may be measured by a method of calculatingthe volume from the weight based on the specific gravity, or a method ofloading the component into a vessel such as a graduated cylindercontaining an appropriate solvent (water, alcohol or the like) thatthoroughly wets the component without dissolving or swelling it, andperforming calculation based on the increased volume.

A bonding aid such as a coupling agent, adhesion enhancer, levelingagent or the like, typically an alkoxysilane derivative or silazanederivative, is preferably added to the adhesive composition of theinvention. This will allow the effect of the invention to be morenotably exhibited, and can also provide satisfactory adhesion andhandleability. Specifically, there is preferably added a compoundrepresented by the following general formula (17).

In formula (22), R⁶, R⁷ and R⁸ each independently represent hydrogen,C1-5 alkyl, C1-5 alkoxy, C1-5 alkoxycarbonyl or aryl, R⁹ representshydrogen or methyl, and p represents an integer of 1-10.

Also in general formula (22), R⁶ is preferably C1-5 alkyl or aryl, R⁷and R⁸ are each independently C2-3 alkoxy and p is 2-4 for moreexcellent adhesive properties and connection resistance. A compoundrepresented by general formula (22) may be used alone, or two or moredifferent ones may be used in combination.

The adhesive composition of the invention may also contain other addedmaterials as suited for the purpose of use. For example, an adhesionenhancer may be added to increase the crosslinking rate of the adhesive.This can further enhance the adhesive strength. Specifically, inaddition to the radical polymerizing compound with a (meth)acryloylgroup, there may be added a compound with a radical polymerizingfunctional group such as allyl, maleimide or vinyl. Specifically, theremay be mentioned N-vinylimidazole, N-vinylpyridine, N-vinylpyrrolidone,N-vinylformamide, N-vinylcaprolactam,4,4′-vinylidenebis(N,N-dimethylaniline), N-vinylacetamide,N,N-dimethylacrylamide, N-isopropylacrylamide and N,N-diethylacrylamide.These adhesion enhancers may be used alone, or two or more differentones may be used in combination.

A flow property enhancer such as a monofunctional (meth)acrylate mayalso be added. This will allow the flow property to be improved.Specifically, there may be mentioned pentaerythritol(meth)acrylate,2-cyanoethyl(meth)acrylate, cyclohexyl(meth)acrylate,dicyclopentenyl(meth)acrylate, dicyclopentenyloxyethyl(meth)acrylate,2-(2-ethoxy)ethyl(meth)acrylate, 2-ethoxyethyl(meth)acrylate,2-ethylhexyl(meth)acrylate, n-hexyl(meth)acrylate,2-hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate,isobornyl(meth)acrylate, isodecyl(meth)acrylate, isooctyl(meth)acrylate,n-lauryl(meth)acrylate, 2-methoxyethyl(meth)acrylate,2-phenoxyethyl(meth)acrylate, tetrahydrofurfuryl(meth)acrylate,2-(meth)acryloyloxyethyl phosphate,N,N-dimethylaminoethyl(meth)acrylate,N,N-dimethylaminopropyl(meth)acrylate and (meth)acryloylmorpholine.These flow property enhancers may be used alone, or two or moredifferent ones may be used in combination.

A rubber-based material may also be used for improved adhesion. It canalso act as a stress reliever. Specifically, there may be mentionedpolyisoprene, polybutadiene, carboxy-terminated polybutadiene,hydroxy-terminated polybutadiene, 1,2-polybutadiene, carboxy-terminated1,2-polybutadiene, hydroxy-terminated 1,2-polybutadiene, acryl rubber,styrene-butadiene rubber, hydroxy-terminated styrene-butadiene rubber,acrylonitrile-butadiene rubber, carboxyl, hydroxyl,acrylonitrile-butadiene rubber having a (meth)acryloyl or morpholinegroup at the polymer terminal, carboxylated nitrile rubber,hydroxy-terminated poly(oxypropylene), alkoxysilyl-terminatedpoly(oxypropylene), poly(oxytetramethylene)glycol, polyolefin glycolsand poly-ε-caprolactone.

From the viewpoint of enhancing adhesion, the rubber-based material ispreferably a rubber-based material containing a highly polar functionalgroup such as cyano or carboxyl on a side chain or at the end, whilefrom the viewpoint of improving the flow property it is even morepreferably a liquid. Specifically, there may be mentioned liquidacrylonitrile-butadiene rubber, liquid acrylonitrile-butadiene rubbercontaining a carboxyl, hydroxyl or (meth)acryloyl group at the polymerterminal and liquid carboxylated nitrile rubber, while the content ofacrylonitrile as the polar group is preferably 10-60 wt % of the entirerubber-based material. These rubber-based materials may be used alone,or two or more different ones may be used in combination.

There may also be included additives such as polymerization inhibitors,which are typically t-butylpyrocatechol, t-butylphenol, p-methoxyphenoland the like. These can also increase the storage stability.

The adhesive composition of the invention may be used in paste form ifit is a liquid at ordinary temperature. When it is a solid at ordinarytemperature, it may be heated into a paste, or dissolved in a solvent toform a paste. The solvent used is not particularly restricted so long asit does not react with the adhesive composition and exhibits sufficientsolubility, but it is preferably one with a boiling point of 50-150° C.at ordinary pressure. If the boiling point is below 50° C. it will tendto volatilize readily at room temperature, thus requiring the radicalpolymerization reaction to be carried out in a sealed environment andtending to limit its scope of use. If the boiling point is above 150°C., it will be difficult to volatilize off the solvent, and sufficientadhesive strength may not be achieved after bonding.

The adhesive composition of the invention may also be used after itsshaping into a film. The method of forming the film may involve coatinga mixture of the adhesive composition and a solvent onto a releasablebase such as a fluorine resin film, a polyethylene terephthalate film ora release sheet, or impregnating a nonwoven fabric or the like with themixture and placing it on a releasable base, and then removing thesolvent to obtain a film. Forming the adhesive composition into a filmin this manner provides the additional advantage of excellenthandleability.

Formation of a film with conductive particles added to the adhesivecomposition of the invention can yield an anisotropic conductive film.The anisotropic conductive film may be placed between opposingelectrodes on a board, for example, and subjected to heating andpressure to bond the electrodes together while forming an electricalconnection. As boards for formation of such electrodes, there may beused inorganic substances such as semiconductors, glass, ceramic or thelike organic materials such as polyimides or polycarbonates, orcombinations thereof such as glass/epoxy.

The adhesive composition of the invention may also be bonded with acombination of heating and pressurization. The heating temperature ispreferably 100-250° C. and more preferably 140-200° C. The pressure maybe in a range that does not damage the adherend, and it is preferably0.1-10 MPa. The heating and pressurization are preferably carried outfor a period in a range of 0.5-120 seconds. Thus, the adhesivecomposition of the invention may be used for bonding of an adherend at,for example, a temperature of 140-200° C. and a pressure of 3 MPa for 10seconds.

The adhesive composition of the invention may also be suitably used as acircuit connecting material because the reaction can be completed in ashort period and the adhesive strength is excellent. For example, whenthe circuit electrode of a first circuit member and the circuitelectrode of a second circuit member are to be electrically connected,the adhesive composition of the invention may be attached to one of thecircuit electrodes with the circuit members situated facing each other,and the other circuit electrode electrically connected thereto byradical polymerization reaction. When the adhesive composition is thusused as a circuit connecting material, electrical connection can beachieved in a short period and the adhesive strength can be stabilizedeven if the process temperature or time for the connection vary. It isalso possible to prevent reduction in the adhesive strength of the curedcircuit connecting material with passage of time. If conductiveparticles are added to the circuit connecting material, it can exhibitelectrical connection anisotropy, for use as an anisotropic conductivecircuit connecting material for circuit electrodes.

When opposing circuit members are bonded by heating under conditionswith a compression time of 10 seconds, a pressure of 3 MPa and a heatingtemperature of 140-200° C., the maximum value of the connectionresistance between the heat bonded connection members in the entireheating temperature range is preferably no greater than 3 times theminimum value. This will allow the process margin to be further widened.

The circuit connecting material may also be used as a circuit connectingmaterial for different types of adherends with different thermalexpansion coefficients. Specifically, it may be used as a circuitconnecting material such as an anisotropic conductive adhesive, silverpaste, silver film or the like, or as a semiconductor element adhesivematerial such as CSP elastomer, CSP underfill material, LOC tape or thelike.

(Connection Structure for a Circuit Member)

A preferred embodiment of a connection structure for a circuit member ofthe invention will now be explained. FIG. 1 is a simplifiedcross-sectional view showing an embodiment of a connection structure fora circuit member according to the invention. As shown in FIG. 1, theconnection structure 1 for a circuit member of this embodiment comprisesa first circuit member 20 and a second circuit member 30 which aremutually opposing, and a circuit connecting member 10 which is formedbetween the first circuit member 20 and second circuit member 30 andelectrically connects them. The first circuit member 20 comprises afirst circuit board 21 and a first circuit electrode 22 formed on themain side 21 a of the circuit board 21. An insulating layer (not shown)may also be formed on the main side 21 a of the circuit board 21.

The second circuit member 30 comprises a second circuit board 31 and asecond circuit electrode 32 formed on the main side 31 a of the secondcircuit board 31. An insulating layer (not shown) may also be formed onthe main side 31 a of the circuit board 31.

The first circuit member 20 and second circuit member 30 are notparticularly restricted so long as they contain the electrodes whichrequire electrical connection. Specifically, there may be mentionedglass or plastic boards, printed circuit boards, ceramic circuit boards,flexible circuit boards, semiconductor silicon chips and the like onwhich ITO is formed for use in liquid crystal display devices, and theymay also be used in combination as necessary. Thus, for this embodimentthere may be used a printed circuit board or a circuit member having anyof various surface conditions, including organic materials such aspolyimides, and metals such as copper or aluminum, or inorganicsubstances such as ITO (indium tin oxide), silicon nitride (SiN_(x)) orsilicon dioxide (SiO₂).

The circuit connecting member 10 comprises an insulating substance 11and conductive particles 7. The conductive particles 7 are situated notonly between the opposing first circuit electrode 22 and second circuitelectrode 32, but also between the main sides 21 a and 31 a. In theconnection structure 1 for a circuit member of this embodiment, thefirst circuit electrode 22 and second circuit electrode 32 areelectrically connected via the conductive particles 7. Thus, connectionresistance between the first circuit electrode 22 and the second circuitelectrode 32 is sufficiently reduced. Consequently, smooth current flowcan be achieved between the first circuit electrode 22 and secondcircuit electrode 32, to allow the function of the circuit to beadequately exhibited. Adding the conductive particles 7 in theproportion mentioned above can create electrical connection anisotropy.

When the circuit connecting member 10 lacks the conductive particles 7,electrical connection is accomplished by direct contact or sufficientproximity between the first circuit electrode 22 and second circuitelectrode 32 for the desired volume of current to flow.

Since the circuit connecting member 10 is composed of a cured circuitconnecting material containing the adhesive composition, the adhesivestrength of the circuit connecting member 10 for the first circuitmember 20 or second circuit member 30 is satisfactorily high, and thecondition can be maintained for prolonged periods. Consequently,long-term reliability of electrical properties can be increased betweenthe first circuit electrode 22 and second circuit electrode 32.

(Semiconductor Device)

An embodiment of a semiconductor device according to the invention willnow be explained. FIG. 2 is a simplified cross-sectional view showing anembodiment of a semiconductor device according to the invention. Asshown in FIG. 2, the semiconductor device 2 of this embodiment comprisesa semiconductor element 50 and a base 60 serving as the support memberfor the semiconductor, and a semiconductor element connecting member 40is provided between the semiconductor element 50 and the base 60 forelectrical connection between them. The semiconductor element connectingmember 40 is laminated on the main side 60 a of the base 60, while thesemiconductor element 50 is further laminated on the semiconductorelement connecting member 40.

The base 60 is provided with a circuit pattern 61, and the circuitpattern 61 is electrically connected via the semiconductor connectingmember 40 on the main side 60 a of the base 60, or directly with thesemiconductor element 50. These are sealed with a sealing material 70 toform the semiconductor device 2.

The material for the semiconductor element 50 is not particularlyrestricted, and there may be used various types including Group 4semiconductor elements such as silicon or germanium, Group III-Vcompound semiconductor elements such as GaAs, InP, GaP, InGaAs, InGaAsP,AlGaAs, InAs, GaInP, AlInP, AlGaInP, GaNAs, GaNP, GaInNAs, GaInNP, GaSb,InSb, GaN, AlN, InGaN or InNAsP, Group II-VI compound semiconductorelements such as HgTe, HgCdTe, CdMnTe, CdS, CdSe, MgSe, MgS, ZnSe orZeTe, and CuInSe (CIS).

The semiconductor element connecting member 40 includes an insulatingsubstance 11 and conductive particles 7. The conductive particles 7 aresituated not only between the semiconductor element 50 and circuitpattern 61, but also between the semiconductor element 50 and the mainside 60 a. In the semiconductor device 2 of this embodiment, thesemiconductor element 50 and circuit pattern 61 are electricallyconnected via the conductive particles 7. Connection resistance betweenthe semiconductor element 50 and circuit pattern 61 is thereforeadequately reduced. Consequently, smooth current flow can be achievedbetween the semiconductor element 50 and circuit pattern 61, to allowthe function of the semiconductor to be adequately exhibited. Inaddition, adding the conductive particles 7 in the proportion mentionedabove can create electrical connection anisotropy.

When the semiconductor element connecting member 40 lacks the conductiveparticles 7, electrical connection is accomplished by direct contact orsufficient proximity between the semiconductor element 50 and circuitpattern 61 for the desired volume of current to flow.

Since the semiconductor element connecting member 40 is composed of thecured adhesive composition containing the adhesive composition, theadhesive strength, of the semiconductor element connecting member 40 forthe semiconductor element 50 and base 60 is satisfactorily high, and thecondition can be maintained for prolonged periods. Consequently,long-term reliability of electrical properties can be increased betweenthe semiconductor element 50 and base 60.

EXAMPLES

The present invention will now be explained in detail by examples, withthe understanding that the invention is not limited to the examples.

(Preparation of Conductive Particles)

A nickel layer was formed on the surface of polystyrene particles to athickness of 0.2 μm, and then a metal layer was formed on the outside ofthe nickel layer to a thickness of 0.02 μm to produce conductiveparticles with a mean particle size of 4 μm and a specific gravity of2.5.

Example 1

There was dissolved 50 parts by weight of a phenoxy resin (thermoplasticresin, average molecular weight: 45,000, trade name PKHC by UnionCarbide) in 75 parts by weight of methyl ethyl ketone to obtain asolution with a solid portion of 40 wt %.

To this solution there were added 25 parts by weight of isocyanuric acidEO-modified diacrylate (radical polymerizing compound, trade name: M-215by Toagosei Co., Ltd.), 20 parts by weight of urethane acrylate (tradename: AT-600 by Kyoeisha Chemical Co., Ltd.), 5 parts by weight of2-(meth)acryloyloxyethyl phosphate (trade name: Light Ester P-2M byKyoeisha Chemical Co., Ltd.), 3 parts by weight of t-hexylperoxy-2-ethylhexanoate (radical polymerization initiator, one-minute half-lifetemperature: 132.6° C., trade name: PERHEXYL O by NOF Corp.) and 1.0part by weight of bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate(radical polymerization regulator, see formula (9)). To the obtainedmixture there were added and dispersed 1.5 vol % of conductive particlesto obtain an adhesive composition (a).

A publicly known coating apparatus was then used to coat the obtainedadhesive composition (a) onto an 80 μm-thick fluorine resin film thathad been surface treated on one side, and the coating was hot-air driedat 70° C. for 10 minutes to obtain a circuit connecting material film(A) with a layer thickness of 15 μm.

Example 2

A circuit connecting material film (B) was obtained in the same manneras Example 1, except that 1 part by weight ofbis(2,2,6,6-tetramethyl-4-piperidyl)sebacate was added instead ofbis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate as the radicalpolymerization regulator.

Example 3

A circuit connecting material film (C) was obtained in the same manneras Example 1, except that 3 parts by weight of diisopropylperoxycarbonate (radical polymerization initiator, one-minute half-lifetemperature: 88.3° C., trade name: PEROYL IPP by NOF Corp.) was addedinstead of t-hexylperoxy-2-ethyl hexanoate as the radical polymerizationinitiator.

Comparative Example 1

A circuit connecting material film (D) was obtained in the same manneras Example 1, except that bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate was not used as a radical polymerization regulator.

Example 4

There was dissolved 40 parts by weight of a phenoxy resin (thermoplasticresin, average molecular weight: 45,000, trade name: PKHC by UnionCarbide) in 60 parts by weight of methyl ethyl ketone to obtain asolution with a solid portion of 40 wt %.

Separately, 450 parts by weight of polybutylene adipate diol (averagemolecular weight: 2000), 450 parts by weight of polyoxytetramethyleneglycol (average molecular weight: 2000) and 100 parts by weight of1,4-butyleneglycol were uniformly mixed in 4000 parts by weight ofmethyl ethyl ketone, and then 390 parts by weight of diphenylmethanediisocyanate was further added prior to reaction at 70° C., to obtain aurethane resin (weight-average molecular weight: 350,000).

Also, 35 parts by weight of the aforementioned solution was mixed with15 parts by weight of the urethane resin to obtain a mixture.

To this solution there were added 15 parts by weight of isocyanuric acidEO-modified diacrylate (radical polymerizing compound, trade name: M-215by Toagosei Co., Ltd.), 30 parts by weight of urethane acrylate (radicalpolymerizing compound, trade name: AT-600 by Kyoeisha Chemical Co.,Ltd.), 5 parts by weight of 2-(meth)acryloyloxyethyl phosphate (radicalpolymerizing compound, trade name: Light Ester P-2M by Kyoeisha ChemicalCo., Ltd.), 3 parts by weight of t-hexylperoxy-2-ethyl hexanoate(radical polymerization initiator, one-minute half-life temperature:132.6° C., trade name: PERHEXYL O by NOF Corp.) and 0.5 part by weightof 2,2,6,6-tetramethylpiperidine-1-oxyl (radical polymerizationregulator). To the obtained mixture there were added and dispersed 1.5vol % of conductive particles to obtain adhesive composition (b).

A publicly known coating apparatus was then used to coat the obtainedadhesive composition (b) onto an 80 μm-thick fluorine resin film thathad been surface treated on one side, and the coating was hot-air driedat 70° C. for 10 minutes to obtain a circuit connecting material film(E) with a layer thickness of 15 μm.

Example 5

A circuit connecting material film (F) was obtained in the same manneras Example 3, except that 0.5 part by weight of4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl was added instead of2,2,6,6-tetramethylpiperidine-1-oxyl as the radical polymerizationregulator.

Comparative Example 2

A circuit connecting material film (G) was obtained in the same manneras Example 3, except that 2,2,6,6-tetramethylpiperidine-1-oxyl was notused as a radical polymerization regulator.

(Evaluation Method)

[Measurement of Adhesive Strength]

The adhesive strengths of the circuit connecting material films (A)-(D)obtained by the methods described above were measured by the 90° peelmethod according to JIS-Z0237, and the variation in adhesive strength atheating temperatures of 150° C., 160° C. and 170° C. was evaluated. Theadhesive strength measuring apparatus used was a TENSILON UTM-4 (peelrate: 50 mm/min, 25° C., product of Toyo Baldwin Co., Ltd.). The resultsare shown in Table 1.

The adhesive strengths of the circuit connecting material films (E)-(G)were measured in the same manner, except that the evaluation wasconducted at heating temperatures of 140° C., 160° C. and 200° C. Theresults are shown in Table 2.

[Measurement of Connection Resistance]

The circuit connecting material films (A)-(D) obtained by the methodsdescribed above were used for electrical connection between a flexiblecircuit board (FPC) having 500 copper circuit wires at a line width of25 μm, a pitch of 50 μm and a thickness of 18 μm, and a glass panel (1.1mm thickness, 20Ω/□ surface resistance) having a 0.2 μm indium tin oxide(ITO) thin-layer formed thereon, over a width of 2 mm using athermocompression bonding apparatus (heating system: constant heating,product of Toray Engineering). The heating and pressing conditions wereheating temperatures of 150° C., 160° C. and 170° C., a pressure of 3MPa and a heating/pressing time of 15 seconds. The connection resistancebetween the electrically connected circuits was measured using amultimeter immediately after bonding and after holding for 120 hours ina high-temperature, high-humidity vessel at 85° C., 85% RH. Theresistance value was expressed as the average of 150 resistance pointsbetween the adjacent circuits (x+3σ). The results are shown in Table 1.

The circuit connecting material films (E)-(G) obtained by the methodsdescribed above were used for electrical connection between a flexiblecircuit board (FPC) having 500 copper circuit wires at a line width of25 μm, a pitch of 50 μm and a thickness of 18 μm, and a glass panel (1.1mm thickness, 20Ω/□ surface resistance) having a 0.2 μm indium tin oxide(ITO) thin-layer formed thereon, over a width of 2 mm using athermocompression bonding apparatus (heating system: constant heating,product of Toray Engineering). The heating and pressing conditions wereheating temperatures of 140° C., 160° C. and 200° C., a pressure of 3MPa and a heating/pressing time of 10 seconds. The connection resistancebetween the electrically connected circuits was measured using amultimeter immediately after bonding and after holding for 168 hours ina high-temperature, high-humidity vessel at 85° C., 85% RH. Theresistance value was expressed as the average of 37 resistance pointsbetween the adjacent circuits (x+3σ). The results are shown in Table 2.

TABLE 1 Adhesive Connection strength (N/m) resistance (Ω) ImmediatelyImmediately Heating after After after After temperature bonding 120 h.bonding 120 h. Example 1 150° C. 1080 930 1.8 2.5 160° C. 1100 955 1.62.5 170° C. 1120 960 1.7 2.8 Example 2 150° C. 1100 1040 2.0 2.4 160° C.1030 980 1.8 2.7 170° C. 1060 980 2.1 2.6 Example 3 150° C. 800 360 2.8≧10 160° C. 680 420 8.4 ≧10 170° C. 535 350 ≧10 ≧10 Comp. 150° C. 1170700 2.4 2.8 Ex. 1 160° C. 815 620 3.8 3.8 170° C. 540 325 ≧10 ≧10

TABLE 2 Adhesive Connection strength (N/m) resistance (Ω) ImmediatelyImmediately Heating after After after After temperature bonding 168 h.bonding 168 h. Example 4 140° C. 670 600 1.6 2.8 160° C. 700 650 1.7 2.9200° C. 780 700 1.9 3.2 Example 5 140° C. 685 630 1.4 2.6 160° C. 720700 1.8 2.5 200° C. 800 720 2.3 3.6 Comp. Ex. 2 140° C. 530 380 3.9 7.0160° C. 600 470 3.2 6.8 200° C. 700 500 12.5 23.4

The circuit connecting material films (A)-(C) of Examples 1 to 3exhibited low variation in adhesive strength, with heating temperaturesof 150-170° C., immediately after bonding and after holding for 120hours in a high-temperature, high-humidity vessel at 85° C., 85% RH,demonstrating that they have satisfactory properties for a wide range ofheating temperatures. In contrast, the circuit connecting material film(D) of Comparative Example 1 which was not according to the inventionexhibited a relatively significant reduction in adhesive strength withhigher heating temperature.

Also, the circuit connecting material films (A) and (B) of Examples 1and 2, which employed radical polymerization initiators havingone-minute half-life temperatures of 90-175° C., exhibited low variationin connection resistance, with heating temperatures of 150-170° C.,immediately after bonding and after holding for 120 hours in ahigh-temperature, high-humidity vessel at 85° C., 85% RH, demonstratingthat they are more preferred modes.

Also, the circuit connecting material films (E) and (F) of Examples 4and 5 exhibited low variation in adhesive strength, with heatingtemperatures of 140-200° C., immediately after bonding and after holdingfor 168 hours in a high-temperature, high-humidity vessel at 85° C., 85%RH, demonstrating that they have satisfactory properties for a widerange of heating temperatures. However in Comparative Example 3, whichdid not employ a radical polymerization regulator of the invention, theconnection resistance value immediately after bonding was high at alltemperatures, while a drastic increase in connection resistance was seenwith heating at 200° C., and after holding for 168 hours in ahigh-temperature, high-humidity vessel at 85° C., 85% RH the increase inconnection resistance was greater than in Examples 4 and 5. The adhesivestrength was also reduced compared to Examples 4 and 5.

When Examples 4 and 5 are compared with Comparative Example 2 in termsof the connection resistance ratio (maximum connectionresistance/minimum connection resistance) immediately after bonding, theratio was 1.2 (1.9 (connection resistance at 200° C.)/1.6 (connectionresistance at 140° C.)) in Example 4 and 1.6 (2.3 (connection resistanceat 200° C.)/1.4 (resistance value at 140° C.)) in Example 5, while theratio was 3.9 (12.5 (resistance value at 200° C.)/3.2 (resistance valueat 160° C.)) in Comparative Example 2.

This demonstrated that using a radical polymerization regulatoraccording to the invention can ensure a wide curing temperature marginand high reliability.

(Shelf Stability)

The circuit connecting material films (A) and (E) obtained in Examples 1and 4 were stored in a vacuum package and allowed to stand at 40° C. for3 days, after which FPC and ITO were thermally bonded under conditionsof 160° C., 3 MPa, 10 sec using the aforementioned thermocompressionbonding apparatus. The adhesive strengths and connection resistances ofthe obtained films were measured according to evaluation methods 1 and2. The results are shown in Table 3.

TABLE 3 Adhesive strength (N/m) Connection resistance (Ω) Before Afterstanding Before After standing standing 40° C., 3 days standing 40° C.,3 days Example 1 1.8 1.8 1080 1030 Example 4 1.6 1.8 670 720

Table 3 shows that the circuit connecting material films (A) and (E) ofExamples 1 and 4 exhibited satisfactory adhesive strength and connectionresistance before and after standing at 40° C., and therefore haveexcellent stability with passage of time.

INDUSTRIAL APPLICABILITY

As explained above, according to the present invention it is possible toprovide an adhesive composition, a circuit connecting material, aconnection structure for a circuit member and a semiconductor devicewhereby curing treatment can be carried out with sufficient speed at lowtemperature, curing treatment can be carried out with a wide processmargin, and adequately stable adhesive strength can be obtained.

What is claimed is:
 1. A circuit-connecting material for electricalconnection between opposing circuit electrodes, wherein the circuitconnecting material comprises an adhesive composition comprising athermoplastic resin, a radical polymerizing compound, a peroxy esterderivative with a one-minute half-life temperature of 90-175° C., and anamine compound represented by the following general formula (1):

wherein R¹ and R² each independently represent hydrogen, hydroxyl, or amonovalent organic group, and X¹, X², X³, and X⁴ each independentlyrepresent hydrogen or C1-C5 alkyl.
 2. The circuit-connecting materialaccording to claim 1, wherein R′ is hydrogen, hydroxyl, C1-C10 alkyl,aryl, C2-C20 alkoxy or a monovalent organic group represented by thefollowing general formula (2):

wherein R³ represents hydrogen or C1-C5 alkyl, R⁴ represents C1-C5ester, benzyl ester, carboxyl or aryl, R⁵ represents hydrogen, C1-C20alkyl, C1-C20 alkoxy, phenoxy, aryl, C1-C20 carbonyloxy,phenylcarbonyloxy or vinyl and n represents an integer of 1-20, wherephenoxy, aryl and phenylcarbonyloxy may be optionally substituted withC1-C5 alkyl.
 3. The circuit-connecting material according to claim 1,wherein the amine compound containsN,N′-bis(3-aminopropyl)ethylenediamine and2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazinecondensate, andpoly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}],a compound represented by the following chemical formula (3):

a compound represented by the following chemical formula (4):

a compound represented by the following chemical formula (5):

a compound represented by the following chemical formula (6):

a compound represented by the following chemical formula (7):

a compound represented by the following chemical formula (8):

a compound represented by the following chemical formula (9):

a compound represented by the following chemical formula (10):

a compound represented by the following chemical formula (11):

wherein R¹⁰ is a group represented by formula (12a) or (12b) below:

a compound represented by the following chemical formula (13):

wherein m represents a positive integer, a compound represented by thefollowing chemical formula (14):

a compound represented by the following chemical formula (15):

a compound represented by the following chemical formula (16):

and a polymer obtained by introducing a substituent represented by thegeneral formula (1) above at a side chain.
 4. The circuit-connectingmaterial according to claim 1, wherein the radical polymerizing compoundhas at least two (meth)acryloyl groups in the molecule.
 5. Thecircuit-connecting material according to claim 1, wherein the peroxyester derivative has a molecular weight of 180-1,000.
 6. Thecircuit-connecting material according to claim 1, which contains theradical polymerizing compound at 50-250 parts by weight, the peroxyester derivative at 0.05-30 parts by weight and the amine compound at0.001-30 parts by weight with respect to 100 parts by weight of thethermoplastic resin.
 7. The circuit-connecting material according toclaim 1, characterized by further comprising conductive particles. 8.The circuit-connecting material according to claim 7, which comprisesthe conductive particles at 0.5-30 parts by weight with respect to 100parts by weight of the thermoplastic resin.
 9. A circuit-connectingmaterial film obtained by forming the circuit-connecting materialaccording to claim 1 into a film shape.
 10. A connecting structure for acircuit member, comprising: a first circuit member having a firstcircuit electrode formed on a main side of a first circuit board, asecond circuit member having a second circuit electrode formed on a mainside of a second circuit board, and a circuit connecting member formedbetween the main side of the first circuit board and the main side ofthe second circuit board, which electrically connects the first circuitelectrode and the second circuit electrode which are positioned oppositeeach other, characterized in that the circuit connecting member is acured product of the circuit-connecting material according to claim 1.